For effectively rendering surface details, many texture-based methods such as normal mapping and displacement mapping were invented to model detailed structures on a surface. Although self-shadow can be achieved by those techniques, most of them support hard shadow or ad-hoc approximation of soft-shadow for the self-shadow effects. In this paper, we present a simple and physically correct method to render soft-shadow in displacement mapped surfaces. Our method first computes a visibility cone map, which stores the average visible ratio of each texel toward a certain direction. Then, during the rendering, the intensity of each pixel on the texture mapped surfaces can be calculated from the overlap between the projected lighting area and the projected visible cone.

為了能更有效率地繪製出物體表面較為細節的結構，許多利用貼圖為手段的方式像是用貼圖改變表面的normal或是用一些height fields取代表面結構的方式因應的被發明。即便這些技術能方便的做到物體表面結構在自身表面上產生的陰影效果，但卻通常只能支援點光源所造成的輪廓明顯銳利的陰影或是用一些不符合物理意義的方式去趨近面積光源所造成的柔和的陰影。
這篇論文中，我們會介紹一個簡單方便的方式改良height fields所取代表面的繪製技術，使之可以做到面積光源產生柔和陰影的效果。首先我們會在height fields每一點預先計算一些錐狀體來簡化每個點的能見區域，將這些錐狀體的角度存成一張貼圖，在繪圖時，就能藉由這些錐狀體中能涵蓋光源面積的比例來計算出每個點可以受到的光照強度。

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